IP Range → CIDR Converter
Convert any arbitrary start–end IP address range into the minimal set of CIDR blocks that covers it exactly. Used for firewall migrations, AWS Security Groups, ACL rewrites, and route summarization.
IP Range Input
Summary
◼ Before◼ CIDR blocks◼ After
CIDR Blocks
| # | CIDR Block | Network | Broadcast | First → Last Host | Total Addresses |
|---|
Why IP Ranges Don't Map to a Single CIDR
CIDR blocks are power-of-2 aligned boundaries. An arbitrary range like 10.0.0.100–10.0.0.200 cannot align to any single boundary, so it requires multiple CIDR blocks — the minimal covering set.
Common Use Cases
- AWS Security Groups: AWS only accepts CIDR notation — convert vendor-supplied ranges instantly.
- Firewall ACLs: OPNsense, Palo Alto, Forcepoint all require CIDR for network objects.
- BGP prefix filtering: Convert customer IP ranges into exact prefixes to permit in a route-map.